I think we'll probably see both QBs in the first week or two, but if we want to realistically compete in conference play, we need to be settled on "the" QB by week 3, imo.
There's nothing wrong with pulling a QB mid game or mid season if he's performing poorly, but unless we seriously plan on drawing up packages for both, then we're going to suffer once we get into the meat grinder of conference play if we're still playing musical chairs - even in practice.
Imo, if either QB takes over sometime in the middle of the season it's likely because something bad has happened, not because it finally "clicked" for the other guy.
I voted for Gebbia because I think he's more of a complete player, I think he offers more flexibility in terms of gameplaning week to week and with potential in-game adjustments. I think he's better suited to use the skill players around him on any given week..... On paper, I look at him as a Joe Ganz type. Solid passer, solid runner, level head, it might look ugly or broken at times, but if everyone else does their jobs, we'll do pretty well. He might not be electric as a runner, but I think he's like Ganz in that he's a grinder, a gamer.
I think AM will get playing time this season, but unless he takes control by week 2 or 3, then I don't think he'll be starting at the end of the season.